1. Field
The present inventions relate generally to hysteroscopic tissue removal systems for the removal of uterine fibroids and other abnormal gynecological tissues and relate more particularly to a novel hysteroscopic tissue removal system having improved fluid management and/or monitoring capabilities.
2. Description of the Related Art
It is believed that uterine fibroids occur in a substantial percentage of the female population, perhaps in at least 20 to 40 percent of all women. Uterine fibroids are well-defined, non-cancerous tumors that are commonly found in the smooth muscle layer of the uterus. In many instances, uterine fibroids can grow to be several centimeters in diameter and may cause symptoms like menorrhagia (prolonged or heavy menstrual bleeding), pelvic pressure or pain, and reproductive dysfunction.
Current treatments for uterine fibroids include pharmacological therapy, hysterectomy, uterine artery embolization, and hysteroscopic resection. Pharmacological therapy typically involves the administration of NSAIDS (non-steroidal anti-inflammatory drugs), estrogen-progesterone combinations, and GnRH (gonadotropin releasing hormone) analogues. However, current pharmacological therapies are largely ineffective and merely palliative.
By comparison, a hysterectomy involves the surgical removal of the uterus from a patient. For this reason, a hysterectomy represents a highly effective way of ridding a patient of uterine fibroids. As a result, several hundred thousand hysterectomies are typically performed annually in the United States to treat uterine fibroids. However, despite their widespread use, hysterectomies also possess certain disadvantages, such as a loss of fertility, sexual dysfunction, and the risks commonly associated with a major surgical procedure, such as hemorrhaging, lesions, infections, pain and prolonged recovery.
Uterine artery embolization involves inserting a catheter into a femoral artery and then guiding the catheter to a uterine fibroid artery. Small particles are then injected from the catheter into the fibroid artery, blocking its blood supply and causing it to eventually shrink and die. Although this procedure is less invasive than a hysterectomy, it often results in pain-related, post-surgical complications. Moreover, the physicians that are trained to perform uterine artery embolization are typically interventional radiologists, as opposed to physicians trained specifically to take care of gynecological problems, whereas the physicians trained specifically to take care of gynecological problems typically do not possess the skill to perform catheter-based uterine artery embolization.
Hysteroscopic resection typically involves inserting a hysteroscope, i.e., an imaging scope, into the uterus transcervically through the vagina and then cutting away the fibroid from the uterus using a device delivered to the fibroid by the hysteroscope. Hysteroscopic resections typically fall into one of two varieties. In one variety, an electrocautery device in the form of a loop-shaped cutting wire is fixedly mounted on the distal end of the hysteroscope—the combination of the hysteroscope and the electrocautery device typically referred to as a resectoscope. The transmission of electrical current to the uterus with a resectoscope is typically monopolar, and the circuit is completed by a conductive path to the power unit for the device through a conductive pad applied to the patient's skin. In this manner, tissue is removed by contacting the loop with the part of the uterus wall of interest. Examples of such devices are disclosed, for example, in U.S. Pat. No. 5,906,615, inventor Thompson, issued May 25, 1999.
In the other variety of hysteroscopic resection, an electromechanical cutter is inserted through a working channel in the hysteroscope. Tissue is then removed by contacting the cutter, which typically has a rotating cutting instrument, with the part of the uterus wall of interest. Examples of the electromechanical cutter variety of hysteroscopic resection are disclosed in, for example, U.S. Pat. No. 7,226,459, inventors Cesarini et al., issued Jun. 5, 2007; U.S. Pat. No. 6,032,673, inventors Savage et al., issued Mar. 7, 2000; U.S. Pat. No. 5,730,752, inventors Alden et al., issued Mar. 24, 1998; U.S. Patent Application Publication No. US 2009/0270898 A1, inventors Chin et al., published Oct. 29, 2009; U.S. Patent Application Publication No. US 2006/0047185 A1, inventors Shener et al., published Mar. 2, 2006; and PCT International Publication No. WO 99/11184, published Mar. 11, 1999, all of which are incorporated herein by reference.
In the above-described varieties of hysteroscopic resection, prior to fibroid removal, the uterus is typically distended to create a working space within the uterus. Such a working space does not normally exist naturally in the uterus because the uterus is a flaccid organ with its walls typically in contact with one another when in a relaxed state. The conventional technique for creating such a working space within the uterus is to administer a fluid to the uterus through the hysteroscope under sufficient pressure to cause the uterus to become distended.
A benefit of the fluid distension is the tamponade effect that the distension fluid provides on resected vascular tissue. Since the distension fluid is typically maintained at a pressure that exceeds the patient's mean arterial pressure (MAP), the fluid pressure provided by the distension fluid prevents the leakage of arterial blood from the resected tissue from flowing or oozing into the uterine cavity. When arterial blood flows or oozes into the cavity, it mixes with the distension fluid and renders visualization more difficult and, if not constrained, the flowing or oozing blood will force the suspension of the procedure. Thus, maintenance of fluid pressure above the intracavity arterial pressure is highly beneficial for the maintenance of a clear visual field.
Examples of the fluid used conventionally to distend the uterus include gases like carbon dioxide or, more commonly, liquids like water or certain aqueous solutions, e.g., a saline or other physiologic solution or a sugar-based or other non-physiologic solution. Because the distending fluid is administered under pressure, which pressure may be as great as 100 mm Hg or greater, there is a risk, especially when vascular tissue is cut, that the distending fluid may be taken up by a blood vessel in the uterus, i.e., intravasation, which uptake may be harmful to the patient. Thus, it is customary to monitor the fluid uptake on a continuous basis using a scale system.
Despite the risks of intravasation, with proper monitoring of fluid uptake, hysteroscopic resection is a highly effective and safe technique for removing uterine fibroids. One shortcoming that has been noted by the present inventors in connection with existing hysteroscopic tissue removal systems, particularly of the electromechanical cutter variety, is that it is often difficult to maintain fluid distension of the uterus during the resection procedure. This is because, during the resection procedure, suction is typically applied to the electromechanical cutter device to draw tissue into the device and to facilitate the removal of the resected tissue from the uterus. However, such suction also typically has the effect of removing some of the distending fluid from the uterus along with the resected tissue. While most systems typically have a pressure sensor that actuates a pump to deliver replacement distending fluid to the uterus when the fluid pressure in the uterus drops due to the loss of distending fluid, the drop in pressure may be precipitous, particularly if a high suction pressure is applied. A steep drop in uterine fluid pressure will result in the leakage of blood into the uterine cavity, causing a loss of visualization and ultimately stoppage of the procedure if the surgeon can no longer properly visualize the treatment site. Moreover, depending on the extent and speed of the drop in uterine fluid pressure, there may be a significant lapse of time before the uterine fluid pressure can be restored to a desired level such that adequate visualization is possible. Such lapses in time are clearly undesirable as they interrupt the resection procedure, as well as lengthen the overall time for the procedure and increase the risk of intravasation.